PROJECT SUMMARY Non-small cell lung cancer (NSCLC) remains the major cause of cancer mortality across the globe, despite exciting advances in immune-based therapies. These therapies, while dramatically effective in some patients, are ineffective in the majority of NSCLC patients. The causes of treatment failure remain incompletely understood, as is the role of the local tumor microenvironment (TME) in influencing tumor growth, both in the presence and absence of these therapies. To better study human tumor-immune interactions and immunotherapeutics, we have developed a humanized mouse model that supports the engraftment of mice bearing a matched human hematopoietic system and tumor from an individual NSCLC patient. In addition, this model is unique in its support of functional myeloid cells as part of the innate immune system. We propose to use these autologously-engrafted humanized NSCLC PDX models to study the TME in detail, employing flow cytometric, immunostaining and single cell genomic analyses to characterize the transcriptional and proteomic states of the cells present. We will correlate tumor growth to specific cell populations identified with these methods, enhancing our understanding of the pathways active in tumor- vs blood-resident immune cells, and identifying established and possibly new networks of immune dysfunction in the TME. Armed with this knowledge, we will probe the pathways active in these patient models using drugs specific to the immune exhaustion and tumor promoting mechanisms we identify. Our goal is to gain a deeper understanding of how the TME and immunotherapeutics interact, and to develop these immune avatar mice as models that may predict a patient?s response to a particular immunotherapy. The principal investigator is a physician-scientist, with a PhD in genetics and post-doctoral and clinical training in Medical Oncology. His career goal is to become an independent investigator studying tumor-immune interactions. The proposed K08 training plan will provide the candidate with mentorship and coursework to build the expertise necessary to execute the proposed project and become independent in the field of translational immuno-oncology.